I don’t think this is something that unusual (or at least I hope so lol). This is someone that played a significant role in your life, that from one day til the next is suddenly not there anymore. For me this felt a bit like a part of my everyday life just died. Although I’m not sure how much you can compare this to the grief from death I feel like there are some similarities.
As others have already said, it does get easier with time, where at some point you will probably notice that you haven’t thought about her for some days and then from there on the times where you think about her get further and further apart.
I know that for me I also had some underlying issues that really exacerbated the situation in a bad way. Therapy helped here so much. Not trying to say that you necessarily need therapy, but if you think that you may also have some underlying issues I really think that this will help immensely.
Hope you can work through this and can get happier with your current situation and partner.
Great song! Always love how bass emphasized they are